you need 6-10 letters

And I notice that you don't have any letter from US government. Usually, you'll need at least 2-3 letters from national labs or centers which represents US government.
The basic rule is to have your source of letter diversified as much as you can. For example, you can have 1-2 letters each from A, B, C university, and 1 from other countries (or 2 from 2 countries), and 2-3 from government.

所有跟帖： 

• 回复：you need 6-10 letters -sourbaby- ♀ (160 bytes) () 06/18/2008 postreply 09:12:55

• 谢谢！我所用的推荐信都来自学校，NIH算是represents US government吗？ -littlepearl- ♀ (126 bytes) () 06/18/2008 postreply 09:43:32

• Yes. NIH算. Also you need 2-3 gov letters even for NIW. -sourbaby- ♀ (237 bytes) () 06/18/2008 postreply 13:00:23